The present disclosure relates to toner compositions for use in xerography. In particular, the present disclosure relates to cold pressure fix toner compositions.
Cold pressure fix toners normally operate in a system employing a pair of high-pressure rollers to fix toner to paper without heating. Among the advantages of such systems are the use of low power and little paper heating. One example of a cold pressure fix toner comprises predominantly wax an ethylene-vinyl acetate copolymer with softening point of 99° C., and a 120° C. softening point polyamide thermoplastic polymer. An example of this approach is shown in U.S. Pat. No. 4,935,324, which is incorporated herein by reference. Another example of a cold pressure fix toner is comprised of a copolymer of styrene with 1-tertiary-butyl-2-ethenyl benzene and a polyolefin wax exemplified for example as Xerox 4060 cold pressure fix toner. Other cold fix toners have been based on a long chain acrylate core produced by suspension polymerization, such as lauryl acrylate. Examples of such compositions are disclosed in U.S. Pat. Nos. 5,013,630 and 5,023,159 which are incorporated herein by reference. Such systems are designed to have a core with a Tg less than room temperature. A hard shell, such as polyurethane prepared by an interfacial polymerization, is disposed about the core in order to keep the liquid content in the core in the toner particle.
Performance issues in designs with high wax content include that they work only at high pressure, such as about 2000 psi or even 4000 psi, which are respectively, 140 kgf/cm2 and 280 kgf/cm2 and even then image robustness can be poor. In the case of long chain acrylate core designs the shell needs to be very thin to break under pressure, but it can be very challenging to prevent the capsules from leaking because the core is typically a liquid at room temperature.
Other material approaches for CPF toners include baroplastics materials comprising nanophase polymeric materials comprised of two components that can become miscible with each other under pressure thereby facilitating flow. Block copolymers have been employed as disclosed in U.S. Pat. No. 8,273,516, wherein the baroplastic resin comprises of a low Tg and a high Tg component that nanophase separate. CPF toners have been prepared based on mixing a crystalline polyester resin and small molecule rosinated ester together with or without an amorphous resin to provide a material that undergoes a phase change from solid to liquid with pressure. Although good fixing properties were obtained, the CPF toners resulted in poor pen-offset, blocking and low charging/electrical performance. CPF toners prepared to date provide modest cold pressure fix performance, and thus there is a continuing need for new CPF toners.